Metal-phosphate binders are used in a number of industrial and non-industrial applications. Such binders may be used to produce adhesives, coatings, and other materials with desired physical, chemical, thermal, and/or electrical properties. For example, such binders may be used to produce adhesives and coatings for high temperature applications or corrosion resistance. In addition, metal-phosphate binders may be used to produce materials that form important structural components of exhaust systems including, for example, catalyst supports and gas absorbers. Further, these binders may be used to produce a variety of useful monolithic, ceramic, and/or composite materials.
In some metal-phosphate binder production processes, the binder is produced by combining one or more metal-ion donors with an electron donor in an acidic solution. However, previously used electron donors may provide slow reactions when used to produce metal-phosphate binder solutions, and as a result, production of useful binders may be very time consuming. In addition, some binder production processes require the use of carbohydrate electron donors, such as sucrose, which may remain in the binder solution after donating electrons. Subsequently, the carbohydrates may be removed by heating, thereby increasing the porosity of the material or otherwise altering the material structure. In some cases, increasing the porosity or other structural properties may produce undesirable changes in material performance.
One method for producing a metal-phosphate binder is described in U.S. Pat. No. 5,620,645, issued to Crumpacker on Apr. 15, 1997 (hereinafter “the '645 patent”). The method of the '645 patent includes mixing chromium oxide with an aqueous ortho-phosphoric acid solution. Common table sugar and alumina are then added, and the mixture is heated while stirring until the reaction is complete. Finally, some of the aqueous solvent may be removed to produce a syrup-like binder.
Although the method of the '645 patent may be used to produce a suitable binder, the method may have several disadvantages. The method of the '645 patent may be time consuming, taking up to twelve hours to produce a batch of binder. In addition, the method of the '645 includes the use of table sugar. Table sugar or table sugar reaction products, which may include one or more carbohydrates, may remain in the binder solution upon completion of the reaction. As described above, the remaining sugar or sugar reaction products may produce undesirable alterations in material structural features. Furthermore, the method of the '645 patent may include the use of one or more metal oxides, which can be volatile at elevated temperatures and may pose certain health risks, including exposure to certain hazardous metal ions.
The present disclosure is directed to overcoming one or more of the disadvantages of the prior art metal-phosphate binders and methods of producing such binders.